In vitro replication of mouse hepatitis virus strain A59.

An in vitro replication system for mouse hepatitis virus (MHV) strain A59 was developed using lysolecithin to produce cell extracts. In extracts of MHV-infected cells, radiolabeled UMP was incorporated at a linear rate for up to 1 h into RNA, which hybridized to MHV-specific cDNA probes and migrated in denaturing formaldehyde-agarose gels to the same position as MHV genomic RNA. The incorporation of [32P]UMP into genome-sized RNA in vitro correlated with the observed increase of [3H]uridine incorporation in MHV-infected cells labeled in vivo. Incorporation of [32P]UMP into genome-sized RNA was inhibited when extracts were incubated with puromycin. The addition to the assay of antiserum to the MHV-A59 nucleocapsid protein N inhibited synthesis of genome-sized RNA by 90% compared with the addition of preimmune serum. In contrast, antiserum to the E1 or E2 glycoproteins did not significantly inhibit RNA replication. In vitro-synthesized RNA banded in cesium chloride gradients as a ribonucleoprotein complex with the characteristic density of MHV nucleocapsids isolated from virions. These experiments suggest that ongoing protein synthesis is necessary for replication of MHV genomic RNA and indicate that the N protein plays an important role in MHV replication.     

Primary structure analysis proves that protein phosphatases 2C1 and 2C2 are isozymes

The two recently discovered forms of protein phosphatase 2C, termed 2C1 and 2C2, were digested with CNBr or trypsin, and several peptides corresponding to two regions of the protein were sequenced. These studies revealed close homology between the two enzymes with 49 identities over the 62 residues that could be compared directly. The results establish that protein phosphatases 2C1 and 2C2 are the products of different genes. The C-terminus of protein phosphatase 2C2 has also been identified.     

The effect of dietary alteration of prostaglandin synthesis on blood pressure and the reversal of hypertension in the one-kidney, one-clip rat

This study examined the effect of diet-induced changes in prostaglandin synthesis on systolic blood pressure in one-kidney, one clip (1k, 1C) hypertensive rats and on the fall in blood pressure after unclipping. It tested the hypothesis that inhibition of prostaglandin synthesis exacerbates hypertension in this model and prevents complete reversal after unclipping. Rats with sustained hypertension within 8 weeks of renal artery clipping were fed synthetic diets supplemented to 20% of total energy with either safflower oil (linoleic acid) or a mixture of cod liver oil (90%) (containing eicosapentaenoic acid) and linseed oil (10%) (containing linolenic acid) for 4 weeks. The latter oil mixture resulted in a predictable reduction in kidney PGE2 and 6-keto PGF1 alpha (hydrolysis product of PGI2), aortic 6-keto PGF1 alpha and serum TXB2. However, at the end of 4 weeks dietary treatment there were no differences in systolic blood pressure between the two diet groups, and the blood pressure fall 24 hours after unclipping was similar. These findings therefore do not support a role for prostanoids in the maintenance or reversal of 1K, 1C hypertension.     

MAJOR CLADES OF THE ANGIOSPERMS

Abstract— Our knowledge of fundamental angiosperm interrelationships is still very incomplete. The absence of a narrowly circumscribed gymnosperm outgroup, ideally the sister group, makes character evaluation, necessary for a cladistic analysis, difficult. According to current views the superorder Magnoliiflorae with a number of other groups, for example the monocotyledons, may represent a complex of families near the base of the angiosperms. Interrelationships of groups within the monocotyledons are much better understood than those between groups within the dicotyledons. A cladogram of monocotyledon orders based on earlier work by R. Dahlgren, H. T. Clifford, and F. N. Rasmussen is presented. A data matrix for a sample of the angiosperms with 61 characters for 49 taxa, mostly magnoliifloran and related families, is presented. The characters are polarized mainly according to the current view that the primitive angiosperm morphotype is a woody dicotyledon with strobiloid flowers. As an alternative the matrix is adjusted following W. C. Burger's conjecture that the primitive angiosperm was a herbaceous monocotyledon with trimerous flowers. Both matrices were run in a computerized parsimony analysis, resulting in numerous equally parsimonious solutions. This result is illustrative of the great homoplasy in the available character information, and also of how little actually is known about fundamental angiosperm interrelationships or phylogeny.     

Relationships among negative life events, physiological reactivity, and health symptomatology

College undergraduates classified as high (n = 25) and low (n = 25) on recent life stress participated in an experiment involving a novel laboratory stressor. Heart rate and pulse arrival time (PAT) were measured during baseline, anticipation, testing, and recovery periods of the experiment. The results did not replicate those obtained by Pardine and Napoli in that high and low life stress subjects did not show differential physiological reactions. In addition, regression analyses failed to demonstrate that physiological reactivity moderated the relationship between life stress and subsequent self-reported psychiatric or physical health symptomatology. The present findings demonstrated neither the stress-buffering effects of physiological reactivity nor a relationship between life stress and reactivity when the latter was conceptualized as an outcome.     

Assignment of orthologous relationships among mammalian alpha-globin genes by examining flanking regions reveals a rapid rate of evolution

In order to study the relationships among mammalian alpha-globin genes, we have determined the sequence of the 3' flanking region of the human alpha 1 globin gene and have made pairwise comparisons between sequenced alpha-globin genes. The flanking regions were examined in detail because sequence matches in these regions could be interpreted with the least complication from the gene duplications and conversions that have occurred frequently in mammalian alpha-like globin gene clusters. We found good matches between the flanking regions of human alpha 1 and rabbit alpha 1, human psi alpha 1 and goat I alpha, human alpha 2 and goat II alpha, and horse alpha 1 and goat II alpha. These matches were used to align the alpha-globin genes in gene clusters from different mammals. This alignment shows that genes at equivalent positions in the gene clusters of different mammals can be functional or nonfunctional, depending on whether they corrected against a functional alpha-globin gene in recent evolutionary history. The number of alpha-globin genes (including pseudogenes) appears to differ among species, although highly divergent pseudogenes may not have been detected in all species examined. Although matching sequences could be found in interspecies comparisons of the flanking regions of alpha- globin genes, these matches are not as extensive as those found in the flanking regions of mammalian beta-like globin genes. This observation suggests that the noncoding sequences in the mammalian alpha-globin gene clusters are evolving at a faster rate than those in the beta-like globin gene clusters. The proposed faster rate of evolution fits with the poor conservation of the genetic linkage map around alpha-globin gene clusters when compared to that of the beta-like globin gene clusters. Analysis of the 3' flanking regions of alpha-globin genes has revealed a conserved sequence approximately 100-150 bp 3' to the polyadenylation site; this sequence may be involved in the expression or regulation of alpha-globin genes.